1. Field of the Invention
The present invention relates to a waterproofing backing adhesive structure, especially a waterproofing backing adhesion for being adhered between the front cover and the display panel that prevents detachment of the waterproofing backing adhesive structure from the front cover or the display panel due to a bubble.
2. Description of the Related Art
There are two major methods of waterproof design for current electronic products. One is by using the installation of an O-type gasket. Though the O-type gasket has the advantage of reuse, it needs a larger space for installation, so it is not suitable for application in small lightweight electronic products. The other is by using a waterproof backing adhesive. A waterproof backing adhesive can be applied in small lightweight electronic products and can provide a good waterproofing effect as well; however, the following problems will occur while it is in use.
Please refer to FIG. 1, which is related to a waterproof backing adhesive structure whose technology has been previous disclosed. Usually in the assembly process of the electronic device 90, production workers will first remove the paper-film on the bottom surface 14a of the backing adhesive 1a, adhere it to the front cover 91 of the electronic device 90, and then remove the paper-film on the upper surface 12a, after which the workers press and glue the display panel 92 of the electronic device 90 to the upper surface 12a of the backing adhesive 1a to make it adhere to the backing adhesive 1a. However, in the process of adhering the backing adhesive 1a, and in the instance of adhering the backing adhesive 1a, if the process of adhesion is not smooth enough to fully expel all air from between the backing adhesive 1a and the front cover 91 or display panel 92, the unexpelled air will be captured between the backing adhesive 1a and the front cover 91 or display panel 92 and will form an bubble 95 (as shown in FIG. 2). Although the existence of the bubble 95 will not immediately affect the usage of the electronic device 90, the bubble 95 will gradually expand and contract under air pressure due to expansion when it is hot, shrinkage when it is cold, or other factors of the backing adhesive 1a, over a long period of use of the electronic device 90 (as shown with an arrow in the figure). Therefore, if the width of the backing adhesive 1a is not wide enough (especially for handheld devices such as mobile phones of small size—if the visible area of the display panel is to be expanded, the width of the backing adhesive needs to be shrunken), it could lead to a local opening between the backing adhesive 1a and the front cover 91 or display panel 92, form a channel for leakage, allow water vapor to easily seep into the leakage, and cause the failure of the backing adhesive, which does not meet the requirements and standards of waterproof and dustproof of the IP (Ingress Protection).